The present invention relates generally to the field of semiconductor device manufacturing and in particular relates to method of defining and forming well isolation surrounding implanted wells in a semiconductor substrate.
As demand for advanced semiconductor devices such as those being often used in smartphones and high-definition television (HDTV) sets, for example, continues to soar and evolve, so do these semiconductor devices continue to scale down in size and scale up in functionality, and complexity of semiconductor manufacturing technologies continue to become more complicated.
For example, different types of semiconductor transistors may be manufactured on a single wafer or substrate. These types of transistors may include n-type transistors, which are manufactured on p-type wells or regions implanted with positive ions in a substrate, and p-type transistors, which are manufactured on n-type wells or regions implanted with negative ions in the same substrate. In order for the p-type transistors and n-type transistors to function properly as they are designed to, without interfering each other, the p-type wells and n-type wells are generally isolated from each other by well isolations that are made between the p-type wells and n-type wells. With the continued scale down and so shrinkage of real estate for each devices, well isolations are required to be formed in very limited spaces between p-type wells and n-type wells. Moreover, these well isolations are preferably made with as few additional manufacturing steps as possible.